FIG. 1 illustrates a point-to-multipoint wireless communication system 100. The system 100 comprises a central node 110 and NU remote nodes 120-iU (iU=1, . . . , NU) with each remote node establishing a bidirectional wireless communication link, e.g. 130, with the central node 110. Examples of such systems include cellular mobile phone systems and wireless local area networks. The central node 110 is referred to herein as an access point (AP) and the remote nodes 120-iU as user terminals (UTs). The component of the wireless link 130 from a UT 120-iU to the AP 110 is called the uplink while the component of the wireless link 130 from the AP 110 to a UT 120-iU is called the downlink. The AP 110 is connected to a core communications network (not shown).
If the AP 110 is equipped with one antenna, the total capacity of the AP 110, herein called the AP cell capacity, is limited by the spectral efficiency of the AP-UT wireless link 130 and the operational frequency bandwidth. For example, if the spectral efficiency of the AP-UT wireless link 130 (irrespective of the number of UTs) is 4 bits/s/Hz and the operational frequency bandwidth available to the AP 110 is 20 MHz, then the AP cell capacity is 80 Mbits/s. This AP cell capacity is shared among multiple UTs 120-iU by each UT establishing a wireless link 130 with the AP 110 using a different frequency (frequency division multiple access, or FDMA), a different timeslot (time division multiple access, or TDMA), a different code (code division multiple access, or CDMA), or a combination of these multiple access schemes. If the system 100 comprises only one UT 120-iU, then the single UT 120-iU can in theory achieve 80 Mbits/s AP-UT wireless link capacity, herein called UT link capacity. However, if the system 100 comprises 20 UTs, then each UT can only in theory achieve 4 Mbits/s on average, irrespective of the different multiple access schemes mentioned above. In practice, the maximum average link capacity achievable for each UT 120-iU is less than this limit due to overheads such as guard bands for FDMA or guard times for TDMA.
A need therefore exists for wireless communication systems that provide AP cell capacity that increases in proportion to the number of user terminals.